One clear sign that your cell phone battery might be dying is that it can no longer hold a charge for long. The amount of time your cell phone battery holds a charge depends on how frequently you use it, and what you use it for. Long conversations, excessive video watching, video game playing and other activities can drain a battery faster than just making short phone calls a few times a day. However, if the battery drops from fully charged to half charged to dead within a day despite not being taxed heavily, odds are it's on its way out. If the battery can hold a charge for only an hour or so with limited use, it's beginning to fail.
If your cell phone works only when it is plugged into a wall outlet, odds are the battery within is dying, if not already dead. If this is the case, you can purchase a replacement battery. Regardless of how old or new the battery is, always check its temperature while it's being charged. If the battery seems to be getting warmer each time you charge it with your charger, it is beginning to die. Batteries should last about two years before showing symptoms of failure, but you should check the temperature every time they charge.
Perhaps the most obvious sign of a failing cell phone battery comes when the phone simply refuses to work. In this case you will not be able to hear any sounds when you press the keys and the display screen will be dark. Hold down the "Power" button on your cell phone for a few seconds or even a minute. If there is any life left in the battery, the phone should eventually turn on. If nothing happens, make sure the battery contacts are clean. If the contacts are dirty or dusty, this can disrupt the charging process. If the contacts are clean and holding down the power button for a period of time does not revive the phone, the battery is failing.
To keep your battery active for as long as possible, avoid leaving your phone on when it's not in use. Try your best to keep phone calls short and---if possible---send text messages instead. Do not charge your cell phone battery daily, but rather every other day. Avoid leaving your cell phone in either extremely high or extremely low temperatures, as both will eventually take a toll on the battery. If possible, use your cell phone while it's charging.